Positive displacement pump



y 2, 1963 R. 5. BRAND 3,095,823

POSITIVE DISPLACEMENT PUMP Filed Aug. 14. 1961 FIG, I

2 Sheets-Sheet 1 I I4 I INVENTOR. RONALD 3 BRAND BY Jw, fa 44M.

ATTORNEYS y 2, 1963 R. 8. BRAND 3,095,823

POSITIVE DISPLACEMENT PUMP Filed Aug. 14, 1961 2 Sheets-Sheet 2 FIG. 3

00 I 84 92 q 4 8 y 88 -90 -l06 C) 6 N 96 EJIA United States Patent Office 3,095,823 Patented July 2, 1963 3,095,823 PGSITIVE DISPLACEMENT PUMP Ronald S. Brand, Westford Road, Eastford, Conn. Filed Aug. 14, 1961, Ser. No. 131,213 6 Claims. (Cl. 103-117) This invention relates to a rotary fluid pump, and deals more particularly with a rotary pump having a positive displacement characteristic.

The general object of this invention is to provide a positive displacement pump which eliminates the need for reciprocating pistons, complicated valve mechanisms, sliding vanes or other similar parts commonly found in conventional positive displacement pumps.

A further object of this invention is to provide a pump of the foregoing character which is of a relatively simple construction, which requires only a relatively small number of parts, and which is relatively inexpensive to manufacture.

A still further object of this invention is to provide a pump of the foregoing character which may be designed as either a fixed displacement or a variable displacement pump without any basic change in the arrangement or cooperation of the various parts thereof.

A still further object of this invention is to provide a pump of the foregoing character which lends itself to a dual-chambered construction and wherein the chambers operate alternatively with one chamber filling while the other discharges, to provide a substantially steady output.

Other objects and advantages of the invention will be apparent from the following description and from the drawings forming a part thereof.

The drawings show preferred embodiments of the invention and such embodiments will be described, but it will be understood that various changes may be made from the constructions disclosed, and that the drawings and description are not to be construed as defining or limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

Of the drawings:

FIG. 1 is "a vertical sectional view taken on a plane passing through the longitudinal axis of a pump embodying the present invention and in which view the two main or driving rotors are positioned by the shaft so that the left-hand operating chamber is at maximum volume while the right-hand operating chamber is at minimum volume.

FIG. 2 is a transverse sectional view taken on the line 22 of FIG. 1.

FIG. 3 is a horizontal sectional view taken on the line 3-3 of FIG. 1, but in which view the shaft has been rotated 90' clockwise, looking toward the left of FIG. 1, so that the two main or driving rotors occupy positions different from that in FIG. 1 and with the result that the volumes of the two operating chambers are equal.

FIG. 4 is a view partly in side elevation and partly in vertical section of a housing employed in a pump comprising a modification of the present invention.

FIG. 5 is an end elevational view of the housing shown in FIG. 4.

Turning now to the drawings, and first particularly referring to FIGS. 1, 2 and 3, the illustrated pump includes a stationary housing 10. The housing may be made as a single integral unit, but in the present case is shown to be made up of two separate end pieces .12 and 14 and an intermediate piece 16-. The three pieces 12, 14 and 16 have cylindrical outer surfaces of substantially the same diameter and are held together in end to end abutting relationship by an oversize locating bolt 18 and five smaller tie bolts 20, 20 as shown in FIGS. 1 and 2. The two end pieces 12 and 14 are each provided with cylindrical bores 22 and 24, respectively, which bores are arranged coaxial with each other and are of substantially the same size. The middle piece 16 is provided with a smaller diametered cylindrical bore 26 which bore passes through the center piece 16 and is located eccentn'eally with respect to the two coaxial bores 22 and 24. The center piece 16, therefore, serves in effect as a partition or wall between the two coaxial bores 22 and 24. Preferably land as shown, but not necessarily, the diameter and location of the eccentric bore 26 is such that the surface of the'bore is at one point tangent with the cylindrical surfaces of the coaxial bores 22, 24. In the illustrated case, as shown in FIG. 2, the point of tangency occurs at the lowermost point of the bores, or at the six oclock position, when the housing is positioned as shown.

Positioned respectively in the two coaxial bores 22 and 24 are two main or driving rotors 38 and 40, respectively. Each of the rotors 38 and 40 is cylindrical in shape and has an outer cylindrical surface which is'substantially the same diameter as the diameter of the associated bore so that the rotor sealingly closes the outer end of the associated bore. The fit between the rotors 38 and 40 and the bores 22 and 24 is, however, such that the rotors 38 and 40 are free to be rotated relative to the housing. The driving rotor 38 has a flat inclined end face 42 which faces inwardly toward the center piece or partition 16, and the rotor 41] has a similar inclined end face 44 which likewise faces inwardly toward the middle piece or partition 16. The two inclined end faces 42 and 44 thus oppose each other and they are positioned in parallel planes. The two rotors 38 and 40 are mounted on a drive shaft 46 which passes axially through the two rotors and through the eccentric bore 26 and are angularly fixed thereto by suitable means such as keys 48 and 50 which are received by registering slots in the drive shaft and the rotors as shown in FIG. 1.

Preferably, and as shown, but not necessarily, the maximum longitudinal or axial length of the cylindrical outer surface of each main rotor is substantially the same as the axial length of its associated housing bore. To hold the rotors 38 and 40 in axially fixed position with respect to the housing 10 each end of the housing is provided with an annular retaining member 52 which is held to the housing by the bolts 18 and 20, 20 as shown in FIG. 1. Each member 52 extends radially inwardly from the associated end piece 12 or 14 and engages the outer end face of the associated rotor to prevent the same from moving out of its associated bore, the outer end face of each rotor being flat and disposed in a plane normal to the axis of rotation. In the illustrated case each retaining member is also formed to include two legs 54, 54 for use in attaching the pump to a supporting structure although other means for supporting the pump may be employed.

Loosely carried by the eccentric bore 26 in the middle piece or partition 16 is a driven rotor 56. The rotor 56 has an outer cylindrical surface of substantially the same diameter as the bore 26 so that the rotor is free to rotate about and reciprocate axially along its center axis which axis is also the axis of the eccentric bore 26. The rotor 56 has two end faces which are flat and inclined to the same degree as the end faces 42 and 44 on the main rotors 38 and 40. The two inclined end faces 58 and 69 are disposed in parallel planes and the length of the rotor 56 is such that the end face 58 flatly engages the end face 42 while the end face 60 simultaneously flatly engages the end face 44. The drive shaft 46 passes through an axial bore 62 in the rotor 56 and is not drivingly connected therewith.

Due to the flat and simultaneous engagement between the end faces of the eccentric rotor 56 and the inclined end faces of the coaxial rotors 38 and 40 the rotor 56 is driven in rotation about its central axis, the axis of the bore 26, when the rotors 38 and 40am rotated by the shaft 46. At the same time, this rotation of the eccentric rotor 56 by the coaxial rotors 38 and 40' will also cause the eccentric rotor to be reciprocated axially relative to the middle piece or partition 16.

The fact that the rotor 56 rotates about and reciprocates along its axis can be observed from FIG. 1 by noting that with the shaft 46 in the position shown, the rotor 56 is moved as far as it will go toward the right. Now, if the shaft 46 is moved 180 in either direction relative to the housing 10, the rotor 56 will be moved toward the left as far as it will go due to a change in the direction of the inclination of the two inclined end faces 42 and 4-4. To allow for this reciprocation of the rotor 56 and the change in the direction of inclination of the end faces 42 and 44' it will be obvious that the rotor 56 will have to rotate 180 about its axis in the same direction as that in which the rotors 38 and 40 are rotated. In FIG. 3 the rotors 38 and 4%) are shown rotated 90 from the positions occupied in FIG. 1 and in FIG. 3 it will be noted that the rotor 56 is located midway between its extreme right and left end positions.

Referring to FIGS. 1 and 3, it will also be noted that the inclined end face 42 of the rotor 38, the surface of the bore 22, the outer cylindrical surface of the rotor 56 and the associated end or wall surface of the partition 16 collectively define an operating chamber 64. It will also be observed that the inclined end face 44 of the rotor 49, the surface of the bore 24, the outer cylindrical surface of the rotor 56 and the associated end surface of the partition 16 likewise define another similar operating chamber 66. The volumes of these two operating chambers are, in turn, cyclically varied by 'the reciprocation of the rotor 56. That is, the reciprocation of the rotor 56 causes the rotor to alternatively move into and out of the partition 16 with respect to each chamber to occupy more orless of the free volume of the chamber. For example, considering the operating chamber 64, as the rotor 56 moves to the right it moves into the partition 16 and occupies less of the chamber 64 so that the volume of the chamber is increased. Likewise, as it moves to'the left it extends out of the partition 16, occupying more of the chamber 64 and therefore decreasing the eifective volume of said latter chamber. As the rotor 38 is moved through one complete revolution the 'rotor 56 is driven through one complete cycle of reciprocation so that the volume of the-chamber 64 is varied I cyclically between its maximum and minimum volumes.

The same general effect holds true for the operating chamber 66 except that the-volume of the chamber 66 increases while the volume of the chamber 64 decreases and decreases while the volume of the chamber 64 increases.

This cyclic variation in the volume of the chambers 64 -and 66 is used to effect a pumping action by providing each of the chambers 64 and 66 with suitable inlet and outlet port means for admitting fluid from a source to the chamber while the volume thereof is increasing and for discharging fluid to a receiver while the volume is decreasing. The inlet and outlet ports for each chamber communicate with the chamber and suitable'valve means are provided for closing and opening the ports in timed relation with the rotation of the driving rotors so that the ports are alternately opened and closed in proper timed sequence to achieve a pumping action. Various suitable inlet and outlet port means may be employed, but preferably the construction is such that the outer cylindrical surfaces of the driving rotors serve as valves i for opening and closing the ports, and such construction is shown in the drawings.

Referring to FIG. 3 and considering specifically the left-hand operating chamber 64, it will be noted that the housing piece 12 is provided with an outlet port 68 and an inlet port '76 comprising circular holes drilled through the housing piece 12. Actually, either the port 68 or the port 7% may be the outlet port and the other the inlet port depending on the direction in which the shaft 46 is rotated, but for the direction of rotation indicated by the arrow A, or clockwise rotation looking toward the left, the port 68 is the outlet port and the port 76 is the inlet port. The inlet port 76 is threaded at its outer end to receive a pipe or conduit 72 which may be connected to a source of fluid for delivering fiuid'to the pump. Likewise, the outlet port 68 is threaded at its outer end to receive a pipe or conduit- 74 which may be connected to a suitable fluid receiver. The inner end of each of'the ports 68 and '70 opens adjacent the surface of the bore 22 and the two ports are located diametrically opposite from each other along a line which passes through the axis of coaxial bores 22 and 24 and which line is perpendicular to the plane passing through both the axis of the coaxial bores and the axis of the eccentric bore 26. In other words, if the plane passing through the axis of the coaxial bores and the axis of the eccentric bore is considered a zero reference, the out et port 63 is located from this plane in one direction about the axis of the coaxial bores while the inlet port 79 is located 90 from this plane in the other direction about the axis of the coaxial bores. The two ports 68 and 70 are also so located axially of the housing so that the inner ends of both will be closed by the outer cylinentirely closes the port 76. As soon as the rotor is rotated in the direction of the arrow A from the position shown in FIG. 1, the port 68 will be at least partially opened to permit the flow of fluid out of the chamber 64 as the volume of the latter decreases.

FIG. 3 shows the position of the rotor 38 after it is rotated 90 from the direction shown in FIG. 1 and from this figure it will be noted that at this time the outlet port 68 is fully opened while the inlet port 70 remains closed. Through the next 90 of rotation the outlet port 68 closes and the inlet port 70 again remains closed so that after the rotor 38 is rotated a full from the position shown in FIG. 1 both of the orts 68 and 76 will once again be closed. Continued rotation of the rotor will then cause the inlet port 79 to open while the outlet port 68 remains closed. As the rotor rotates from the 180 position back to the position shown in HG. 1 the inlet port 70 is first fully opened and then returned to its fully closed position. From this it will be seen that the outlet port is opened, or at least partly opened, while the volume of-the chamber 64 is decreasing, with the inlet port 7% being at the same time held closed, and that the outlet port 68 is held closed and the inlet port 70 opened, or at least partially opened, to permit the fiow of fluid into the chamber while the volume thereof is increasing. This opening and closing of the ports 68 and 7% therefore cooperates with the increasing and decreasing nature of the volume 64 to cause a pumping action, the fluid first flowing into the chamber 64 through the inlet port 79 and then being discharged through the outlet port 68.

The arrangement of ports for the chamber 66 is substantially the same as that for the chamber 64. That is, for the direction of rotation of the shaft 66 shown by the arrow A in FIG. 1, the chamber 66 has an inlet port "78 and an outlet port '76, which ports are formed by openings in the housing piece 14 and which ports communicate respectively with supply and discharge pipes or conduits 82 and 89. The ports 76 and 78 are located diametrically opposite from one another in the same manner as the ports 68 and 70 and are so located axially of the housing piece 14 as to be alternately opened and closed in timed relation to the rotation of the shaft 46 by the outer surface of the driving rotor 40 in the same manner as the ports 68 and 70 are opened and closed by the driving rotor 38. The ports 76 and 73, therefore, cooperate with the operating chamber 66 to provide a pumping action.

The operation of the pump shown in FIGS. 1, 2 and 3 is such that the operating chambers 64 and 66 operate in opposition to one another so that when the volume of one chamber is increasing the volume of the other chamber is decreasing. Accordingly, when one chamber is filling the other chamber is discharging and the rate of discharge is substantially uniform throughout the discharge portion of the operating cycle of each chamber. As soon as one chamber completes its discharge the other operating chamber begins to discharge. Thus, by connecting the two outlet conduits 74 and 80 to a single line or receiver, a substantially continuous and steady output may be obtained from the pump.

Although the pump shown in FIGS. 1, 2 and 3 is a dual chambered pump, various features of the invention may be applied as well to a single chambered pump, if desired. For example, referring to FIGS. 1 and 3, and considering the operating chamber 64, it will be noted that as far as this chamber is concerned the purpose of the driving rotor 46 is to urge the eccentric rotor 56 toward the driving rotor 38 so that the end face 58 of the eccentric rotor is maintained in flat engagement with the end face 42 of the driving rotor. Therefore, if it is desired to build only a single chambered pump suitable means different from the driving rotor 40 may be used to urge the rotor 56 into engagement with the driving rotor 38.

The pump shown in FIGS. 1, 2 and 3 has a fixed displacement, a given volume of fluid being discharged with each complete rotation of the shaft 46. The eccentricity of the rotor 56 relative to the axis of the coaxial bores 22 and 24, among other things, determines the displacement of the pump, and therefore a variable displacement pump may be provided for by constructing the housing of the pump in such a manner as to'permitthe center piece to be moved radially to shift the eccentricity of its bore. A housing for such a variable displacement pump is shown, for example, in FIGS. 4 and 5. Referring to these figures, the housing there shown consists of two end pieces 84 and 86 provided with coaxial bores 88 and 90 respectively, which bores serve to receive driving rotors such as the rotors 38 and it) in the pump of FIGS. 1, 2 and 3. At their opposed inner ends the housing pieces 84 and 86 are provided with radially extending rectangular flanges 92 and 94, respectively.

The two flanges 92 and 94 have axially extending portions 6 and 98 formed along each of their longer edges and the two portions 96 and 98 on each side of the housing engage one another so that the flanges 92 and 94 are held in axially spaced relationship. The two housing pieces 84 and 86 are, in turn, held in connected relationship by two connecting members ltit) and W2 which extend between the flanges 92 and 94 shown in FIGS. 4 and 5 and which are held thereto by suitable fastening means. The two flanges 92 and 94 together with their axially extending portions 96 and 98 define a box-shaped guide chamber for receiving-a correspondingly shaped middle housing piece or partition 104. The partition 164, except for being box-shaped rather than cylindrical, is generally similar to the intermediate piece 16 of the pump of FIGS. 1, 2 and 3 and is provided with a bore 106 for receiving a driven rotor such as the rotor 56. Unlike the housing piece 16, however, the member 104 is movable in 6 the guide chamber formed by the flanges 92 and 94 and the flange portions 96 and 5 8. For the purpose of effecting movement of the member 164, a stem 108 is connected thereto which stem may, in turn, be operated by any suitable positioning means. In FIG. 5 the member 164 is shown moved to its lowermost position relative to the housing pieces 84 and 86. At this position the bore 106 has maximum eccentricity relative to the axis of the coaxial bores 88 and 90. As the stem 108 is moved upwardly the member 104 is likewise moved upwardly and the bore 166 is moved closer to axial alignment with the axes of the bores 83 and 90. As the eccentricity of the bore 166 decreases the displacement of the pump likewise decreases, and when the bore 106 is truly axially aligned with the bores 88 and the pump will have zero displacement.

The invention claimed is:

1. A fluid pump comprising a housing having a cylindrical bore, a first cylindrical rotor of substantially the same diameter as said bore rotatively supported at a fixed axial position in said bore in coaxial relationship therewith and sealingly closing one end thereof, said rotor having a flat end face facing the other end of said bore and which end face is inclined relative to the common axis of said bore and said first rotor, wall means fixed relative to said housing and closing said other end of said bore, a second cylindrical rotor of smaller diameter than said bore loosely mounted in said wall means with its axis arranged eccentric to said common axis of said bore and said first rotor, said second rotor being both rotatable about and reciprocable along said eccentric axis relative to said housing and also extending beyond said wall means toward said first rotor and having an inclined flat end face which flatly engages said inclined end faceof said first rotor, said inclined face of said first rotor, thesurface of said housing bore, the surface of said wall means, and the outer cylindrical surface of said second rotor collectively defining an operating chamber, means for urging sad second rotor toward said first rotor so that said two inclined faces are maintained in flat engagement with each other and so that said second rotor is accordingly rotated and reciprocated relative to said housing into and out of said wall means as said first rotor is rotated, the reciprocationv of said second rotor into and out of said wall means serving to cyclically vary the volume of said operating chamber, inlet means adapted for connection to a source of flud and operable to permit fluid to pass from said source to said operating chamber while the volume of the latter is increasing and to prevent fluid from passing in the reverse direction while said volume is decreasing, and outlet means adapted for con nection to a receiver and operable to permit fluid to pass from said operating chamber to said receiver while said volume is decreasing and to prevent said fluid from passing in the reverse direction when said volume is increasing.

2. A pump as defined in claim 1 further characterized by said inlet means comprising an inlet port formed in said housing and having an inner end which opens adjacent the surface of said housing bore and which inner end is so located as to be in communication with said operating chamber while said operating chamber volume is increasing and closed by the outer surface of said first rotor while said operating chamber volume is decreasing, and by said outlet means comprising an outlet port formed in said housing and having an inner end which opens adjacent the surface of said housing bore and which latter inner end is so located'as to be in communication with said operating chamber while said operating chamber volume is decreasing and closed by the outer surface of said rotor while said operating chamber volume is increasing.

3. A fluid pump comprising a housing having two coaxial cylindrical bores separated by a partition having a smaller diametered cylindrical bore extending between said two coaxial bores and eccentrically arranged relative thereto, a shaft extending through said housing concentrically with said two coaxial bores, two cylindrical driving rotors fixed to said shaft each of which rotors is disposed in a respective one of said coaxial bores and has a diameter substantially equal to the diameter of the associated bone so as to sealingly close said bore, said two rotors having opposed faces disposed in parallel planes which planes are inclined relative to the axis of said shaft, and a third cylindrical driven rotor received by said eccentric partition bore and having a diameter substantially equal to that of said bore so that said partiti'on supports the same for rotation about and reciprocation along its longitudinal axis, said third rotor having an axial bore through which said shaft loosely passes and having two inclined and parallel end faces which respectively flatly engage the opposingend faces of said two rotors so that said third rotor is rotated about and reciprocated along its longitudinalaxis as saidtwo rotor-s are rotated by said shaft, the innersurface of each of said coaxial bores, the inclined end face of the associated driving rotor, the associated surface of said partition, and the outer cylindrical surface of that portion of said driven rotor which extends beyond said partition and toward said latter driving. rotor defining an operating chamber the volume of which varies cyclically as said drivenrotor reciprocates, and fluid inlet and outlet means communicating with each of said opera-ting chambers and including valve means operable in timed relation to the rotation of said shaft toalternatively permit and prevent the passage of fluid into and out ofsaid operating chambers in such a manner as to achieve a pumping action.

v 4. A pump as defined in claim 3 further characterized by said partition being separate from the remainder of said'honsing, and means on said housingsupporting said partition for movement radially with respect to said co axial bores to change the eccentricity of said driven rotor relative to said coaxial bores and to thereby vary the displacement of said pump.

5. A fluid pump comprising. a housing having two coaxial cylindrical bores separated by a partition having a smaller diametered cylindrical bore extending between said two coaxial bores and eccentrically arranged relative thereto, a shaft extending through said housing conoentricallywith said two coaxial bores, two cylindrical driving rotors fixed to said shaft each of which rotors is disposed in a respective one of said coaxial bores and has a diameter substantially equal to the diameter of the associated bore so as to sealingly close said bore, said two rotors having opopsed faces disposed in parallel planes which planes are inclined relative to the axis of said shaft,

and a third cylindrical driven rotor received by said eccentric-partition bore and having a diameter substantially equal to that of said bore so that said partition supports the same for rotation about and reciprocation along its longitudinal axis, said third rotor having an axial bore through which said shaft loosely passes and having two inclined and parallel end faces which respectively flatly engage the opposing end faces of said two rotors so that said third rotor is rotated about. and reciprocated along its longitudinal axis as said two rotors are rotated by said shaft, the inner surface of eachof said coaxial bores, the inclined end face of the associated driving rotor, the associated surface of said partition, and the outer cylindrical surface of that portion of said driven rotor which extends beyond said partition and toward said latter driving rotor defining an operating chamber the volume of which varies cyclically as said driven rotorreciprocates, and means defining an inlet and an outlet port for each of said operating chambers each of which ports passes through said housing and has an inner end adjacent the surface of the n L). associated coaxial bore which is opened and closed by the cylindrical outer surface of the associated driving rotor as the latter is rotated, the inner end of the inlet port of each chamber being so located as to be open when the volume of the associated operating chamber is increasing and closed when the volume is decreasing and the inner end of the outlet port of each chamber being so located as to be closed when the volume of the associated operating chamber is increasing and open when the volume is decreasing.

6. A fluid pump comprising a housing having two c0- axial cylindrical bores separated by a partition having a smaller diametered cylindrical bore extending between said two coaxial bores and eccentrically arranged relative thereto, a shaft extending through said housing concentrically withsaid two coaxial bores, two cylindrical driving rotors fixed to said shaft each of which rotors is disposed in a respective one of said coaxial bores and has a diameter substantially equal to the diameter of the associated bore so as to sealingly close said bore, said two rotors having opposed faces disposed in parallel planes which planes are inclined relative to the axis of said shaft, and a third cylindrical driven rotor received by said eccentric partition bore and having a diameter substantially equal to that of said bore so that said partition supports the same for rotation about and reciprocation along its longitudinal axis, said third rotor having an axial bore through which said shaft loosely passes and having two inclined and parallel end faces which respectively flatly engage the opposing end faces of said two rotors so that I said third rotor is rotated about and reciprocated along its longitudinal axis as said two rotors are rotated by said shaft, the inner surface of each of said coaxial bores, the inclined end face of the associated driving rotor, the associated surface of said partition, and the outer cylindrical surface of that portion of said driven rotor which extends beyond said partition and toward said latter driving rotor defining an operating chamber the volume of which varies cyclically as said driven rotor 'reciprocates, and means defining an inlet and an outlet port for each of said operating chambers each of which ports passes through said housing and has an inner end adjacent the surface of the associated coaxial bore which is opened and closed by the cylindrical outer surface of the associated driving rotor as the latter is rotated, the inlet and outlet ports of each chamber being located substantially diametrically opposite from each other along a line passing through the axis of said coaxial bores and perpendicular to a plane passing through both said axis of said coaxial bores and the axis of-said eccentric bore and being further so located axially of said housing that when the associated driving rotor is at either the angular position corresponding to maximum chamber volume or the angular position corresponding to minimum chamber volume both said ports will be closed and that when said rotor is some angular distance from either of said two positions one or the other ofsaid ports will be open.

References Cited inthe file of this patent UNITED STATES PATENTS 

1. A FLUID PUMP COMPRISING A HOUSING HAVING A CYLINDRICAL BORE, A FIRST CYLINDRICAL ROTOR OF SUBSTANTIALLY THE SAME DIAMETER AS SAID BORE ROTATIVELY SUPPORTED AT A FIXED AXIAL POSITION IN SAID BORE IN COAXIAL RELATIONSHIP THEREWITH AND SEALINGLY CLOSING ONE END THEREOF, SAID ROTOR HAVING A FLAT END FACE FACING THE OTHER END OF SAID BORE AND WHICH END FACE IS INCLINED RELATIVE TO THE COMMON AXIS OF SAID BORE AND SAID FIRST ROTOR, WALL MEANS FIXED RELATIVE TO SAID HOUSING AND CLOSING SAID OTHER END OF SAID BORE, A SECOND CYLINDRICAL ROTOR OF SMALLER DIAMETER THAN SAID BORE LOOSELY MOUNTED IN SAID WALL MEANS WITH ITS AXIS ARRANGED ECCENTRIC TO SAID COMMON AXIS OF SAID BORE AND SAID FIRST ROTOR, SAID SECOND ROTOR BEING BOTH ROTATABLE ABOUT THE RECIPROCABLE ALONG SAID ECCENTRIC AXIS RELATIVE TO SAID HOUSING AND ALSO EXTENDING BEYOND SAID WALL MEANS TOWARD SAID FIRST ROTOR AND HAVING AN INCLINED FLAT END FACE WHICH FLATLY ENGAGES SAID INCLINED END FACE OF SAID FIRST ROTOR, SAID INCLINED FACE OF SAID FIRST ROTOR, THE SURFACE OF SAID HOUSING BORE, THE SURFACE OF SAID WALL MEANS, AND THE OUTER CYLINDRICAL SURFACE OF SAID SECOND ROTOR COLLECTIVELY DEFINING AN OPERATING CHAMBER, MEANS FOR URGING SAID SECOND ROTOR TOWARD SAID FIRST ROTOR SO THAT SAID TWO INCLINED FACES ARE MAINTAINED IN FLAT ENGAGEMENT WITH EACH OTHER AND SO THAT SAID SECOND ROTOR IS ACCORDINGLY ROTATED AND RECIPROCATED RELATIVE TO SAID HOUSING INTO AND OUT OF SAID WALL MEANS AS SAID FIRST ROTOR IS ROTATED, THE RECIPROCATION OF SAID SECOND ROTOR INTO AND OUT OF SAID WALL MEANS SERVING TO CYCLICALLY VARY THE VOLUME OF SAID OPERATING CHAMBER, INLET MEANS ADAPTED FOR CONNECTION TO A SOURCE OF FLUD AND OPERABLE TO PERMIT FLUID TO PASS FROM SAID SOURCE TO SAID OPERATING CHAMBER WHILE THE VOLUME OF THE LATTER IS INCREASING AND TO PREVENT FLUID FROM PASSING IN THE REVERSE DIRECTION WHILE SAID VOLUME IS DECREASING, AND OUTLET MEANS ADAPTED FOR CONNECTION TO A RECEIVER AND OPERABLE TO PERMIT FLUID TO PASS FROM SAID OPERATING CHAMBER TO SAID RECEIVER WHILE SAID VOLUME IS DECREASING AND TO PREVENT SAID FLUID FROM PASSING IN THE REVERSE DIRECTION WHEN SAID VOLUME IS INCREASING. 